Drive waveform for gas discharge display/memory panel

ABSTRACT

There is disclosed a gas discharge display/memory panel which has opposing electrode arrays with insulating dielectric charge storage members, the arrays being oriented so as to define a plurality of discharge units or cells, the panel being operated by the application of a sustaining voltage, the writing of a particular unit being effected by the application of a writing voltage to one electrode of the unit and a similar writing voltage to the opposing electrode of the unit, the two writing voltages being algebraically added across the unit from a near zero slope base or plateau, the amplitude of the base being substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of the writing voltage applied to either opposing electrode alone being insufficient to write any unit in the panel.

United States Patent 1 [191 Petty et al.

[ DRIVE WAVEFORM FOR GAS DISCHARGE DISPLAY/MEMORY PANEL [75] Inventors: William D. Petty, Perrysburgh;

David E. Liddle, Toledo, both of Ohio [73] Assignee: Owens-Illinois, lnc., Toledo, Ohio [22] Filed: Oct. 12, 1971 [21] App]. No.: 188,481

Primary Examiner-Nathan Kaufman Attorney, Agent, or Firm- Donald Keith Wedding; Jim

Zegeer 5/ MIX,

[ 1 Apr. 2, 1974 t [57] ABSTRACT There is disclosed a gas discharge display/memory panel which has opposing electrode arrays with insulating dielectric charge storage members, the arrays being oriented so as to define a plurality of discharge units or cells, the panel being operated by the application of a sustaining voltage, the writing of a particular unit being effected by the application of a writing voltage to one electrode of the unit and a similar writing voltage to the opposing electrode of the unit, the two writing voltages being algebraically added across the unit from a near zero slope base or plateau, the amplitude of the base being substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of the writing voltage applied to either opposing electrode alone being insufficient to write any unit in the panel.

10 Claims, 5 Drawing Figures PATENTED APR zlsm 3 801861 SHEEI 1 BF 2 \1 Ii PRIOR ART IAIENIEDAPR 2 m 3.801.861

SIIEEI 2 IIF 2 INTERFACE 8 ADDRESSING CIRCUIT DRIVE WAVEFORM FOR GAS DISCHARGE DISPLAY/MEMORY PANEL BACKGROUND OF THE INVENTION This invention relates to multiple gas discharge display/memory panels or units which have an electrical memory and which are capable of producing a visual display or representation of data such as numerals, letters, radar displays, aircraft displays, binary words, educational displays, etc.

Multiple gas discharge display and/or memory panels of one particular type with which the present invention is concerned are characterized by an ionizable gaseous medium, usually a mixture of at least two gases at an appropriate gas pressure, in a thin gas chamber or space between a pair of opposed dielectric charge storage members which are backed by conductor (electrode) members, the conductor members backing each dielectric member typically being appropriately oriented so as to define a plurality of discrete discharge volumes, each constituting a discharge unit.

In some prior art panels the discharge units are additionally defined by surrounding or confining physical structure such as by cells or apertures in perforated glass plates and the like so as to be physically isolated relative to other units. In either case, with or without the confining physical structure, charges (electrons, ions) produced upon ionization bf the gas of a selected discharge unit, when proper alternating operating potentials are applied to selected conductors thereof, are collected upon the surfaces of the dielectric at specifically defined locations and constitute an electrical field opposing the electrical field which created them so as to terminate the discharge for the remainder of the half cycle and aid in the initiation of a discharge on a succeeding opposite half cycle of applied voltage, such charges as are stored constituting an electrical memory.

Thus, the dielectric layers prevent the passage of substantial conductive current from the conductor members to the gaseous medium and also serve as collecting surfaces for ionized gaseous medium charges (electrons, ions) during the alternate half cycles of the AC. operating potentials, such charges collecting first on one elemental or discrete dielectric surface area and then on an opposing elemental or discrete dielectric surface area on alternate half cycles to constitute an electrical memory.

An example of a panel structure containing nonphysically isolated or open discharge units is disclosed in US. Pat. No. 3,499,167 issued to Theodore C. Baker, et al.

An example of a panel containing physically isolated units is disclosed in the article by D. L. Bitzer and H. G. Slottow entitled The Plasma Display Panel A Digitally Addressable Display With Inherent Memory, Proceeding of the Io int Computer Conference, IEEE, San F'rifi'ciscbfcal," W 541-547. Also reference is made to US. Pat. No. 3,559,l90.

In the fabrication of the panel, a continuous volume of ionizable gas is confined between a pair of dielectric surfaces backed by conductor arrays typically forming matrix elements. The cross conductor arrays may be orthogonally related (but any other configuration of conductor arrays may be used) to define a plurality of opposed pairs of charge storage areas on the surfaces November. 1966," pp.

of the dielectric bounding or confining the gas. Thus, for a conductor matrix having H rows and C columns the number of elemental discharge volumes will be the product I! X C and the number of elemental or discrete areas will be twice the number of elemental discharge volumes.

In addition, the panel may comprise a so-called monolithic structure in which the conductor arrays are created on a single substrate and wherein two or more arrays are separated from each other and from the gaseous medium by at least one insulating member. In such a device the gas discharge takes place not between two opposing members, but between two contiguous or adjacent members on the same substrate.

It is also feasible to have a gas discharge device wherein some of the conductive or electrode members are indirect contact with the gaseous medium and the remaining electrode members are appropriately insulated from such gas, i.e., at least one insulated electrode.

In addition to the matrix configuration, the conductor arrays may be shaped otherwise. Accordingly, while the preferred conductor arrangement is of the crossed grid type as shown herein, it is likewise apparent that where a maximal variety of two dimensional display patterns is not necessary, as where specific standardized visual shapes (e.g., numerals, letters, words, etc.) are to be formed and image resolution is not critical, the conductors may be shaped accordingly.

The gas is one which produces visible light or invisible radiation which stimulates a phosphor (if visual display is an objective) and a copious supply of charges (ions and electrons) during discharge. In an open cell Baker, et al. type panel, the gas pressure and the electric field are suffici'ent to laterally confine charges generated on discharge within elemental or discrete dielectric areas within the perimeter of such areas, especially in a panel containing non-isolated units.

As described in the Baker, et al. patent, the space between the dielectric surfaces occupied by the gas is such as to permit photons generated on discharge in a selected discrete or elemental volume of gas to pass freely through the gas space and strike surface areas of dielectric remote from the selected discrete volumes, such remote, photon struck dielectric surface areas thereby emitting electrons so as to condition other and more remote elemental volumes for discharges at a uniform applied potential.

With respect to the memory function of a given discharge panel, the allowable distance or spacing between the dielectric surfaces depends, inter alia, on the frequency of the alternating current supply, the distance typically being greater for lower frequencies.

While the prior art does disclose gaseous discharge devices having externally positioned electrodes for initiating a gaseous discharge, sometimes called electrodeless discharge, such prior art devices utilized frequencies and spacings or discharge volumes and operating pressures such that although discharges are initiated in the gaseous medium, such discharges are ineffective or not utilized for charge generation and storage at higher frequencies; although charge storage may be realized at lower frequencies, such charge storage has not been utilized in a display/memory device in the manner of the Bitzer-Slottow or Baker, et al. invention.

The term memory margin is defined herein as where V, is the half amplitude of the smallest sustaining voltage signal which results in a discharge every half cycle, but at which the cell is not bi-stable and V is the half amplitude of the minimum applied voltage sufficient to sustain discharges once initiated.

It will be understood that the basic electrical phenomenon utilized in this invention is the generation of charges (ions and electrons) alternately storable at pairs of opposed or facing discrete points or areas on a pair of dielectric surfaces backed by conductors connected to a source of operating potential. Such stored charges result in an electrical field opposing the field produced by the applied potential that created them and hence operate to terminate ionization in the elemental gas volume between opposed or facing discrete points or areas of dielectric surface. The term sustain a discharge" means producing a sequence of momentary discharges, at least one discharge for each half cycle of applied alternating sustaining voltage, once the elemental gas volume has been fired, to maintain alternate storing of charges at pairs of opposed discrete areas on the dielectric surfaces.

Thus in practice, a periodic sustaining voltage sufficient to operate the panel is applied to the opposing electrode arrays, the waveform of such sustaining voltage being rectangular, square, sinusoidal, trapezoidal, triangular, or of any other periodic geometric form or shape. As described in copending U.S. Pat. application Ser. No. 60,402, filed Aug. 3, 1970, having the same assignee as the instant application, one-half of the sustaining voltage may be applied to one electrode array and the other half may be applied at 180 phase or opposite polarity to the opposing electrode array, the two applied sustaining voltages being algebraically added across the unit. Likewise, all of the sustaining voltage may be applied to only one electrode array.

The sustaining voltage is sufficient to operate the panel; that is, sufficient to maintain all of the units or cells in the panel in an off or on state. A unit in the off state is one to which there has not been applied a writing voltage whereas a unit in the on state has received a writing voltage. A unit in the on state is one which has been discharged by the application of the writing voltage such that wall charges are formed and stored on the dielectric charge storage surface(s) of the unit.

In the operation of a multiple gas discharge display/- memory device which contains opposing electrode arrays, the writing of a particular unit or cell is usually effected by applying a writing voltage to one electrode of the cell and a similar writing voltage to the opposing electrode of the cell, the phase of each addressing voltage being such that the two addressing voltages are algebraically added, for example as disclosed and claimed in copending U.S. Pat. application Ser. No. 699,170, filed Jan. 19, 1968, by William E. Johnson and Larry J. Schmersal, also assigned to the assignee of the instant application.

If the writing voltages are derived from the same source, each is equal to the other in magnitude with each therefore representing one half of the total writing voltage for the cell.

Furthermore, each opposing electrode of the cell typically serves as an electrode for other cells, especially in an x y electrode matrix arrangement also known as a column-row electrode matrix. In such a matrix arrangement, a writing voltage is applied to one x-axis (row) electrode and a similar writing voltage is applied to a y-axis (Column) electrode, the two writing voltages being algebraically combined across the cell formed by the intersection of the x-axis electrode and the y-axis electrode. Thus the selection of a particular cell to be addressed is effected by the application of writing voltages to the proper x and y electrodes, e.g., as determined by the appropriate electronic circuitry hardware. 7

When a particular x or y electrode is written, the applied writing voltage may be sufficient to turn-on" a particular cell site even though a corresponding writing voltage is not applied to the opposing electrode of that particular cell site; that is, when writing voltages are applied to the opposingelectrodes of a selected cell, the voltage applied to either electrode may be sufficient to write other cells (not intended to be written). Thus because of non-uniformities in the panel construction, manufacture, etc., one or more cells may be written by only one electrode.

In other words, a fraction or part of the total writing voltage for a to-be-written cell will inherently be applied to other not-to-be-written cells having a locus along the x-electrode and other not-to-be-written cells having a locus along the .y-electrode, such fraction of the total writing voltage being sufficient to turn-on one or more of the not-to-be-written cells. Where the fraction of the writing voltage applied to each opposing electrode of a particular cell is equal, such fraction is therefore one half and the phenomenon of turning on not-to-be-written cells is known as half-select.

In accordance with the practice of this invention, there is provided a process for operating a multiple gaseous discharge panel so as to minimize or eliminate the writing of not-to-be-written cells.

More particularly, this invention comprises a process for operating a multiple gaseous discharge display/- memory panel whereby one writing voltage is applied to one electrode of a panel cell and another writing voltage is applied to the opposing electrode of the same cell, the two applied writing voltages being algebraically added across the cell from a near zero slope base.

or plateau, the amplitude of the base being substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of the writing voltage qpplied to either opposing electrode alone being insufficient to write any unit in the panel.

In the practice of this invention, the writing voltages may be of any suitable waveform, such as broadly defined hereinbefore for the sustaining voltage. It is also contemplated that each writing voltage may be of the same or different waveform. Likewise, it is contemplated that each writing voltage may be of the same or different waveform as that of the sustaining voltage.

In one preferred embodiment, each writing voltage is of a rectangular waveform.

In accordance with one further embodiment of this invention, the x and y writing voltages are of the same magnitude.

In accordance with still another embodiment, the x and y writing voltages are of different magnitude.

In the prior art writing voltages have been algebrically added to the top of the sustaining voltage. One such prior art embodiment is illustrated in FIG. 1 wherein there is shown a sustaining voltage S of a rectangular or square waveform and two writing voltages, W,, and W,,, of a rectangular or square waveform algebraically added to the top of the sustaining voltage.

In FIGS. 2 and 3, there are illustrated two embodiments of the invention at bar.

FIG. 4 is a partially cut away plan view of a gaseous discharge display/memory panel as disclosed in the aforementioned U. S. Pat. No. 3,499,167.

FIG. 5 is a cross sectional view (enlarged, but not to proportional scale since the thickness of the gas line, dielectric members and conductor rays have been charged for purposes of illustration) taken along line 55 of FIG. 4.

FIGS. 4 and 5 illustrate a' gaseous discharge display/- memory panel to which the invention has particular utility. As there illustrated, a pair of dielectric films or coatings or 11, separated by a thin layer or volume of a gaseous medium 12 which produces a copious supply of charges alternately collectable on the surfaces of the dielectric members at opposed or facing elemental or discrete areas X and Y defined by the conductor matrix on non gas contacting sides of the dielectric members. Each dielectric member presents large opening surface areas and a plurality of pairs of X and Y areas. The dielectric members are formed on and supported by non-conductive support members 16 and 17, at leat one of which passes light produced by the discharge line in the elemental gas volumes. These are preferably transparent glass members to which the conductor arrays 13 and 14 have been applied in the manner described in said US. Pat. No. 3,499,l67. The support plates carrying the conductor array 13 and 14 and the dielectric coating thereon l0 and 11 are secured in spaced relation by spacer sealant 15. The electrodes in the aray are driven from an interface and addressing circuit 19 in accordance with the embodiments of the present invention.

In FIG. 2 there is shown a sustaining voltage S with the writing voltages W, and W, being algebraically added from a zero slope plateau separate from the sustaining voltage.

In FIG. 3 there is shown a sustaining voltage S" with the writing voltage W", and W", being algebraically added from a zero slope plateau which is on the lower portion of the sustaining voltage.

Other embodiments of this invention, not illustrated by FIGS. 2 and 3, are also contemplated.

In all embodiments of this invention, including those illustrated by FIGS. 2 and 3, the writing voltages, e.g., W, and W',,, may be ofthe same or different magnitude. Likewise, W, and W, may be selected from te same or different waveform, although square or rectangular waveform is preferred for both.

In all embodiments of this invention, including those illustrated by FIGS. 1 and 2, the magnitude of either writing voltage alone, e.g., W, or W',,, is insufficient to write (discharge) any unit in the panel.

In the preferred practice of this invetion, the magnitude of each writing voltage, e.g., W or W,,, is equal to or less than the magnitude of the sustaining voltage, e.g., S.

We claim:

1. In a process for operating a multiple gas discharge display/memory panel having opposed electrode arrays and at least one insulating dielectric charge storage member, the arrays being oriented so as to define a plurality of discharge cells, and wherein periodic sustaining voltages and writing voltage pulses are applied to the electrode arrays so as to operate the panel, the writing voltage pulses being selectively applied, the improvement comprising, at selected times, and at each cell in said panel, producing a near zero slope voltage plateau, which is greater than zero volts, in said sustaining voltage and during the step of entering information to said panel wherein one writing voltage pulse is applied to one electrode of a discharge cell and a similar writing voltage pulse is applied to the opposing electrode of the cell, said writing voltage pulses being simultaneously applied to the opposing electrode of the cell, respectively, and at a time such that the two wriring voltages being algebraically added across the cell occurs during said zero slope plateau so as to cause a discharge in the selected cell, causing the amplitude of the voltage plateau to be substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of the writing voltage applied to either opposed electrode alone being insufficient to write any cell in the panel.

2. The invention of claim 1 wherein the two writing voltages are of the same magnitude.

3. The invention of claim 1 wherein the two writing voltages are of a different magnitude.

4. The invention of claim 1 wherein at least one of the two writing voltages has a rectangular waveform.

5. The invention of claim 1 wherein the two writing voltaesa are algebriacally added from a zero slope plateau separate from the sustaining voltage.

6. The invention of claim 1 wherein the two writing voltages are algebraically added from a zero slope plateau which is a part of the sustaining voltage.

7. The invention of claim 1 wherein each writing voltage has a magnitude equal to or less than that of the sustaining voltage.

8. In a process for operating a multiple gas discharge display/memory panel comprising an ionzable gaseous medium in a gas chamber formed by a pair of opposed dielectric material charge storage members backed by electrode members, the electrode members behind each dielectric material member being transversely oriented with respect to the electrode members behind the opposing dielectric material member so as to define a plurality of discharge cells, and wherein a periodic sustaining voltage is continuously applied to all of the cells of the panel and writing voltage are applied to selected cells so as to discharge such cells, the improvement which comprises, producing a near zero voltage slope plateau condition in said periodic sustaining voltage, applying one writing voltage to one electrode of a discharge cell and applying a similar writing voltage to the opposing electrode of the cell such that the two writing voltages are algebraically added across the cell during said near zero slope plateau so as to cause a discharge in the cell, the amplitude of said near zero slope plateau being greater than zero volts and substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, the magnitude of each writing voltage being equal to or less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of either writing voltage alone being insufficient to write any cell in the panel.

9. The invention of claim 8 wherein the two writing voltages are of a different magnitude.

10. The invention of claim 9 wherein at least one of the two writing voltages has a rectangular waveform. 

1. In a process for operating a multiple gas discharge display/memory panel having opposed electrode arrays and at least one insulating dielectric charge storage member, the arrays being oriented so as to define a plurality of discharge cells, and wherein periodic sustaining voltages and writing voltage pulses are applied to the electrode arrays so as to operate the panel, the writing voltage pulses being selectively applied, the improvement comprising, at selected times, and at each cell in said panel, producing a near zero slope voltage plateau, which is greater than zero volts, in said sustaining voltage and during the step of entering information to said panel wherein one writing voltage pulse is applied to one electrode of a discharge cell and a similar writing voltage pulse is applied to the opposing electrode of the cell, said writing voltage pulses being simultaneously applied to the opposing electrode of the cell, respectively, and at a time such that the two wriring voltages being algebraically added across the cell occurs during said zero slope plateau so as to cause a discharge in the selected cell, causing the amplitude of the voltage plateau to be substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of the writing voltage applied to either opposed electrode alone being insufficient to write any cell in the panel.
 2. The invention of claim 1 wHerein the two writing voltages are of the same magnitude.
 3. The invention of claim 1 wherein the two writing voltages are of a different magnitude.
 4. The invention of claim 1 wherein at least one of the two writing voltages has a rectangular waveform.
 5. The invention of claim 1 wherein the two writing voltaesa are algebriacally added from a zero slope plateau separate from the sustaining voltage.
 6. The invention of claim 1 wherein the two writing voltages are algebraically added from a zero slope plateau which is a part of the sustaining voltage.
 7. The invention of claim 1 wherein each writing voltage has a magnitude equal to or less than that of the sustaining voltage.
 8. In a process for operating a multiple gas discharge display/memory panel comprising an ionzable gaseous medium in a gas chamber formed by a pair of opposed dielectric material charge storage members backed by electrode members, the electrode members behind each dielectric material member being transversely oriented with respect to the electrode members behind the opposing dielectric material member so as to define a plurality of discharge cells, and wherein a periodic sustaining voltage is continuously applied to all of the cells of the panel and writing voltage are applied to selected cells so as to discharge such cells, the improvement which comprises, producing a near zero voltage slope plateau condition in said periodic sustaining voltage, applying one writing voltage to one electrode of a discharge cell and applying a similar writing voltage to the opposing electrode of the cell such that the two writing voltages are algebraically added across the cell during said near zero slope plateau so as to cause a discharge in the cell, the amplitude of said near zero slope plateau being greater than zero volts and substantially less than the maximum amplitude achieved by the total applied sustaining voltage in one period, the magnitude of each writing voltage being equal to or less than the maximum amplitude achieved by the total applied sustaining voltage in one period, and the magnitude of either writing voltage alone being insufficient to write any cell in the panel.
 9. The invention of claim 8 wherein the two writing voltages are of a different magnitude.
 10. The invention of claim 9 wherein at least one of the two writing voltages has a rectangular waveform. 